Flexible well drill collar



July 5, 1955 J. s. M CUNE ET AL 2,712,436

FLEXIBLE WELL DRILL COLLAR 2 Sheets-Sheet l mil 4? Filed March 51, 1952d HN ($0 MCU/VE,

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United States Patent FLEXIBLE WELL DRILL COLLAR .lohn S. McCune andWilliam E. Hanks, Long Beach, Calif., assignors to Oilwell Drain HoleDrilling Co., 7 Long Beach, Calif., a corporation of CaliforniaApplication March 31, 1952, Serial No. 279,557

9 Claims. (Cl. 25528) This invention has to do with equipment fordrilling well bores diverted at such angularities from the initialstraight hole, as to necessitate the use of a flexible drill stringsection or drill collar. Such equipment particularly is adaptable forthe drilling of so-called drain holes or bores, which are divertablewithin a Wide range of angularities so as to be capable of oil-drainingthe formation from any of selected locations about the main bore. Theinvention is concerned primarily with the structural features andoperative advantages of the flexible drill string section or drillcollar.

The present drill collar may be characterized in common with priorflexible drill shafts of this type, as comprising a series of tubularsections having interlocking end lobular projections giving adjacentsections capacity for relative lateral movcemnt, and imparting suchgeneral flexibility to the drill collar throughout its length, as willpermit great angular deflection of the bit and the course of the drainhole.

One of our major objects is to provide an improved arrangement oflobular interconnections between the drill collar sections that willpermit their relative lateral swinging movement in either of right angleplanes at the same location longitudinally of the drill collar.Specifically the invention contemplates the formation, as by torchcutting out of a single. stand of pipe, inter-section joints eachcomprising four lobes spaced at ninety degrees and positionedlongitudinally of the pipe in essentially the same transverse plane, thelobes on one section interfitting with companion lobes on the adjacentsection so that the sections may swing relatively about either of twopairs of diametrically spaced lobes and corresponding recesses.

A further feature of the invention is the shaping of the lobes so as togive curved surface interengagement of the end surfaces of the sections,while maintaining for the benefit of maximum bearing strength, surfacesof relatively great extent and lesser curvature at the end faces of thelobes and bases of the recesses, as compared with the extent andcurvature of the side faces of the lobes and recesses.

Also contemplated is a lobe formation giving the drill Fatented July 5,1955 Fig. 5 is a developed view illustrating the particular shapecharacteristics of the interlocking lobes; and

Fig. 6 is a cross-section on line 66 of Fig. 3.

Referring first to Figs. 1 and 2, the drilling equipment is shown to berun down in the Well bore 10 and to comprise a drill string whichincludes the upper standard drill pipe 1.1 extending up to the groundsurface, and the flexible drill collar 12 carrying at its lower end anappropriate drill bit 13. It may be desirable for the drill collar tooperate within and out of a tubular sheath generally indicated at 14which serves the dual functions of a housing for the drill collar, andof a carrier for the whipstock 15. The structural and operativerelationships of the drill collar and its sheath are more particularlydealt with in our Patent No. 2,667,332, issuedlanuary 26, 1954.

Referring to Figs. 2a and 2b, the drill collar 12 is con; nected to thepipe string 11 by way of a tubular sub 16, the upper threaded box end ofwhich receives pin 17 of the tool joint 13. The lower pin end 19 of thesub is threaded into the uppermost tubular section 20 of the drillcollar. The drill collar 12 may consist of a single length or stand ofpipe from which are cut the later described lobular joint sections, or asingle drill collar assembly may include a plurality (typically 3 or 4)of pipe stands or lengths 12a. and 12b interconnected as by the righthand threaded joint at 21.

The bottom drill collar section 22 has a pin end threaded at 23 with aknuckle joint generally indicated at 2-; which forms a flexibleconnection between the drill collar and the bit 13. The knuckle joint isshown to comprise a tubular body 25 containing a concave seat 26 engagedby the spherical head 27 of the knuckle 28. The latter has a stem 29threaded into shank 30 of the drill bit. The head 27 containsdiametrically opposed arcuate grooves 51 which receive the inner ends ofpins 32 carried by the body 25, so that the knuckle is capable ofuniversal movement. Upward displacement of the knuckle head from itsseat 26 is limited by engagement with the concave face 33 of theretaining insert 34, up ward displacement of which is limited byengagement with the end of drill collar section 22 at 35. As will beunderstood, upon breaking the joint at 23 and disconnecting the bit fromthe knuckle 28, the latter may be removed from the body 25 upwardlythrough its bore 36. Fluid circulation from the tubular drill collar tothe bit 13 occurs by way of bore 37 within insert 34, and an alined borein knuckle 23. By-passing of circulation fluid around the outside of theinsert may be prevented by applying to the insert a rubber seal ring 49which is engaged against the bore wall 36. Below the knuckle collar suchunbalanced characteristics under longitudinal 7 load, as will create atendency for the drill collar to deflect at its lower end and thusfacilitate directed deflection of the drill bit. 1

The invention has various additional features and objects all of whichwill be most readily understood from the following detailed descriptionof an illustrative embodiment shown by the accompanying drawings, inwhich:

Fig. l is a general view showing the flexible drill collar and outersheath assembly run in the well;

Figs. 2a and 2b are enlarged sectional and vertically continuing viewsof the drill collar, bit and sheath assemy;

Fig. 3-is an enlarged view showing in elevation one of the multiple lobeflexible joints in the drillcollar;

Fig. 4 is a cross-section on line 4-4 of Fig. 3;

joint, the bit shank is shown to carry spiral flights 41 enengageablewith the formation to properly guide and stabilize the bit.

The invention is more particularly concerned with the structural make-upof the drill collar 12 and the interlocking relation between itsrelatively movable sections. Between the top and bottom sections 26 and22, the drill collar includes a series of intermediate sections 42,interconnected at vertically spaced locations 4-3 in a manner such that,at each of those locations, adjacent sections are capable of relativelateral or swinging movement in two different vertical planes which arespaced apart circularly about the drill collar and which passessentially through the axis of the collar. As best illustrated in Figs.3 and 5, each joint at 43 is formed by four lobes 44 projecting at 90spacing from the adjacent ends of the interconnected sections 42 so thatthe lobes on one section are received within the correspondingly shapedrecesses between the lobes on the adjacent section. As particularlyshown by the developed view in Fig. 5, each lobe 44 has an end face 45of relatively greater arcuate locking lobes hole, will retain itsoriented position.

extent and lesser degree of curvature, and side faces 46 of relativelylesser arcuate extent and greater curvature. As illustrative, assumingthe sections 42 to be cut from pipe having an outside diameter of fiveinches, and an inside diameter of two inches, the end faces 45 of thelobes may be cut on a radius of two inches through an arcuate extent ofabout 60 degrees between points a and b; and each side face 46 may becut on an arc of /8 inch radius through an extent of about llO degrees.So shaped, the lobes are given load-assuming bearing faces 45 ofrelatively great arcuate extent and area, and therefore greater Wear andabrasion resistance under the com pressive forces axially applied to orassumed by the drill collar during its operations. As illustrated inFig. 4, the edges of the lobes 44 are tapered inwardly at the jointsections with such clearances existing at 47 between all opposed edgesof the lobes, as will assure the relative movability of theinterconnected sections 42. In this connection the invention is believedto mark the first instance in which it has been proposed to so provideor arrange interlocking lobular projections on flexible drill collarsections so that adjacent sections are relatively movable in the two 90spaced planes of each pair of diametrically opposed lobes, at the sametransverse plane or location along the drill collar.

Since it is desired to produce in cooperation with the later describedwhipstock, lateral deflection of the bit and lower end of the drillcollar in response to force applied downwardly and axially of the drillcollar, it is advantageous that adjacent sections 42 have an unbalancedrelation in the sense that the downwardly applied load tends to swingone section relative to the other about one or the other pair of thediametrically opposed lobes 44. Stated otherwise, it is desirable thatthere be at least slight variance in the bottom support given onediametrically opposed pair of depending lobes 44, as against the otherpair, so that the sections will tend to fulcrum initially about thepoint of end engagement between .the first mentioned pair. Thisunbalanced relation may be effected in different ways as by forming theend faces 45a of alternate lobes 44:: at slightly greater length thanthe corresponding faces of the remaining pair of lobes 44 (assuming therecesses receiving all the lobes 44 and 44a to have the same depth), orby hard facing the end surfaces 45a so that because of their greaterwear resistance, the lobe so treated will tend to retain their initialdimensions as against greater wear of the alternate untreated lobes, andtherefore become fulcrum-points as the interlocking surfaces of thedrill collar undergo wear.

Wearing and abrasion of the drill collar as by reason 'ofits engagementwith the later described sheath 14, may be minimized by providing eachor some of the sections 42 with anti-friction means at locations betweenthe inter- Thus as illustrated in Fig. 2b, a typical form ofanti-friction means 48 may consist of a rubbot link 49 seated within asur ace recess 56 in the sec tion 42, and held thereto as by cementingor the grip of the rubber.

Referring again to Figs. 1 and 2a, the sheath 14 is shown to comprise atubular body 51 having upper and lower sections 52 and 53 interconnectedby left-hand threaded joint at 54. As Fig. 1 shows, the length of thesheath is sufficient to contain the full length of the drill collaranddrill bit as the'asscmbly is being lowered. into the well. At itslower end the'sheath is connected at 55 to a tubular whipstock body 56having a side opening 57 at the bottom of'which is a solid angulardeflecting or whipstocking face 58. The bottom of the whipstock may besuitably supported as by a stand 59 carrying an anchor or shoe 60 whichwhen set and oriented in the bottom of the As illustrated in Fig. 2a,the sub 16 carries a plurality of circularly spaced lugs or ribs 61which are receivable between lugs 62 formed on the lower end of atubular insert 63 in the upper end of the sheath. Initially the drillstring is releasably held against downward movement relative to thesheath by a shear pin 64 threaded through the sheath and insert 63 intothe sub 16. 1

Provision is made for maintaining closed circulation from the drill pipe11 through the flexible drill collar 12 to the bit 13, by way of arubberhose 65 contained in the drill collar bore and terminally retainedwithin the end sections 20 and 22 of the drill collar in any suitablemanner. Merely as illustrative, the upper end hose coupling 65 is shownto be connected by fitting 67 with a tubular adaptor 68 which is seateddownwardly against the shoulder 69. The lower end of the hose is shownto have a.

floating connection with the drill collar section 22 within its bore 70,as by way of fitting71 connecting the hose coupling 72 with a tubularinsert 73.

In a drain hole drilling operation the drill collar, sheath andwhipstock assembly may be set on bottom as shown in Fig. l andappropriately oriented to position the whipstoch face 58 for deflectionof the bit in the desired direction. Thereafter, sufiicient load isapplied to the drill string to shear pin 64 and thus permit downwardmovement of the drill collar within thesheath to the point of engagementof the drill bit 13 with the whipstock face 58 and the formation at theside of the well bore opposite the whipstock face. Drilling is thenstarted, with the bit and drill collar being progressively deflected ina direction and at an angle corresponding to the orientation'andangularity of the whipstock face. The deflected bore 10a thus may bedrilled to a distance corresponding to the length of the drill stringfrom the bit to the uppermost drill collar section 29. Upon completionof'the drilling, the drill collar and bit may beretracted back into thesheath and the entire assembly pulled from the well, if only a shingledrain hole 10a is to be drilled, or the whipstock may be reset at adifferent oriented position for drilling of a second drain hole in adifferent direction. In the latter event, the drill string is raised tothe Fig. 2a position of interengagement between lugs 61 and 62, and thewhipstock is raised off bottom and oriented in a different direction,following which the previously described drilling procedure may berepeated.

Should it be desired to leave the whipstock in the well tional structureof the sheath 51 permits removal of the' drill string separately fromthe whipstock. With the drill string elevated to the Fig. 2a position,right-hand rotation of the drill unscrews the joint at 54, freeing theupper sheath section 52 for removal from the well with the drill string.

We claim:

1. A flexible well drill collar comprising a series of tubular sectionseach having at one end two pairs of projecting curved edge lobesreceived within corresponding recesses in the end of an adjacentsection, the lobes of each being diametrically opposed and the pairsbeing arranged at 90 degree spacing about the axis of the section, andthe-lobes of both pairs terminating in about the same transverse planeof the section so that adjacent sections have relative universalmovement at the same location ongitudinally of the drill collar, bothends of each section having continuous alternately convex and concavecurvatures defining said lobes and recesses, each lobe having a reducedwidth neck, and the individual lobes hav- 'ing end bearing edges curvedessentially circularly at a v75 in the end of an adjacent section, thelobes of each pair being diametrically opposed and the pairs beingarranged at 90 degree spacing about the axis of the section, the lobesof both pairs terminating in about the same transverse plane of thesection so that adjacent sections have relative universal movement atthe same location longitudinally of the drill collar, and one pair oflobes being slightly longer than the other pair so that the sectionsconnected thereby tend to be unbalanced under longitudinal compression.

3. A flexible Well drill collar comprising a series of tubular sectionseach having at one end two pairs of projecting curved edge lobesreceived within corresponding recesses in the end of an adjacentsection, the lobes of each pair being diametrically opposed and thepairs being arranged at 90 degree spacing about the axis of the section,the lobes of both pairs terminating in about the same transverse planeof the section so that adjacent sections have relative universalmovement at the same location longitudinally of the drill collar, bothends of each section having continuous alternately convex and concavecurvatures defining said lobes and recesses, and one pair of lobes beingslightly longer than the other pair so that the sections connectedthereby tend to be unbalanced under longitudinal compression.

4. A flexible Well drill collar comprising a series of tubular sectionseach having at one end two pairs of projecting curved edge lobesreceived within corresponding recesses in the end of an adjacentsection, the lobes of each pair being diametrically opposed and thepairs being arranged at 90 degree spacing about the axis of the section,the lobes of both pairs terminating in about the same transverse planeof the section so that adjacent sections have relative universalmovement at the same location longitudinally of the drill collar, eachlobe having a reduced width neck, the end bearing edge of the lobehaving circular curvature at a greater radius and the continuing sideedges of the lobe being curved at a smaller radius, and one pair oflobes being slightly longer than the other pair so that the sectionsconnected thereby tend to be unbalanced under longitudinal compression.

5. A flexible well drill collar comprising a series of tubular sectionseach having at one end a pair of diametrically opposed curved edge lobesreceived within corresponding recesses in an end of an adjacent sectionto form a pivotal joint, a successive joint including a similar pair oflobes and recesses arranged angularly about the drill collar axisrelative to the first mentioned pair of lobes, each lobe having areduced width neck, the individual lobes having end bearing edges curvedsubstan- 6 lar pair of lobes and recesses arranged angularly about thedrill collar axis relative to the first mentioned pair of lobes, eachlobe having a reduced width neck, certain of said lobe pairs beingslightly longer than other angularly ofi'set pairs so that the sectionstend to be unbalanced under longitudinally applied compression.

7. A flexible well drill collar comprising a series of tubular sectionseach having at one end a pair of diametrically opposed curved edge lobesreceived within corresponding recesses in an end of an adjacent sectionto form a pivotal joint, a successive joint including a similar pair oflobes and recesses arranged angularly about the drill collar axisrelative to the first mentioned pair of lobes, each lobe having areduced width neck, the end bearing edge of the lobe having circularcurvature at a greater radius and the continuing side edges of the lobebeing curved at a smaller radius, certain of said lobe pairs beingslightly longer than other angularly oifset pairs so that the sectionstend to be unbalanced under longitudinally applied compression.

8. A flexible well drill collar comprising a series of tubular sectionseach having at one end two pairs of projecting curved edge lobesreceived within corresponding recesses in the end of an adjacentsection, the lobes of each pair being diametrically opposed and thepairs be:

ing arranged at 90 degree spacing about the axis of the section, and thelobes of both pairs terminating in about the same transverse plane ofthe section so that adjacent sections have relative universal movementat the same location longitudinally of the drill collar, the end edgesof one pair of opposed lobes being curved difierently than thecorresponding edges of the other relatively angularly ofiset pair sothat the sections tend to be unbalanced under longitudinal compression.

9. A flexible Well drill collar comprising a series of tubular sectionseach having at one end a pair of diametrically opposed curved edge lobesreceived within corresponding recesses in an end of an adjacent sectionto form a pivotal joint, a successive joint including a similar pair oflobes and recesses arranged angularly about the drill collar axisrelative to the first mentioned pair of lobes, each lobe having areduced width neck, and the end bearing edges of certain pairs ofopposed lobes being curved difierently from the corresponding edges ofother relatively angularly offset pairs so that the sections tend to beunbalanced under longitudinal compression.

References Cited in the file of this patent UNITED STATES PATENTS1,314,601 McCaskey Sept. 2, 1919 1,739,756 Granville Dec. 17, 19291,814,183 Patterson July 14, 1931 1,854,339 Lamb Apr. 19, 1932 2,515,366Zublin July 18, 1950 FOREIGN PATENTS 81,017 Switzerland May 1, 1919

